1248746 - 5.51% tpaint (win8) e10s regression on mozilla-inbound (v.47) from push 7acb1edc3f91 (Wed Feb 10 2016)

Status: RESOLVED FIXED

(Core :: JavaScript: GC, defect)

Description

[Joel Maher ( :jmaher ) (UTC -8)]

Talos has detected a Firefox performance regression from push 7acb1edc3f91. As author of one of the patches included in that push, we need your help to address this regression.

This is a list of all known regressions and improvements related to the push:

https://treeherder.allizom.org/perf.html#/alerts?id=122

On the page above you can see an alert for each affected platform as well as a link to a graph showing the history of scores for this test. There is also a link to a treeherder page showing the Talos jobs in a pushlog format.

To learn more about the regressing test(s), please see:
https://wiki.mozilla.org/Buildbot/Talos/Tests#tpaint

Reproducing and debugging the regression:

If you would like to re-run this Talos test on a potential fix, use try with the following syntax:
try: -b o -p win64 -u none -t other-e10s[Windows XP,Windows 8] --rebuild 5  # add "mozharness: --spsProfile" to generate profile data
(we suggest --rebuild 5 to be more confident in the results)

To run the test locally and do a more in-depth investigation, first set up a local Talos environment:
https://wiki.mozilla.lorg/Buildbot/Talos/Running#Running_locally_-_Source_Code

Then run the following command from the directory where you set up Talos:
talos --develop -e <path>/firefox -a tpaint --e10s

Making a decision:
As the patch author we need your feedback to help us handle this regression.
*** Please let us know your plans by Friday, or the offending patch(es) will be backed out! ***

Our wiki page outlines the common responses and expectations:
https://wiki.mozilla.org/Buildbot/Talos/RegressionBugsHandling

Comment 1

[Joel Maher ( :jmaher ) (UTC -8)]

this is a hard bug to pinpoint:
https://treeherder.allizom.org/perf.html#/graphs?series=[mozilla-inbound,c6caad67b3eb993652e0e986c372d016af4d6c8b,1]&series=[mozilla-central,c6caad67b3eb993652e0e986c372d016af4d6c8b,1]&highlightedRevisions=5bf10cf78faf&highlightedRevisions=7acb1edc3f91&zoom=1454717288946.7788,1455147369691.8767,246.35687732342006,261.04089219330854

you can see we have a lot of retriggers showing a big range of data, but I determined that 7acb1edc3f91 is the one where we didn't post in the ~250 range.  This is pgo only which makes it odd.

I have lower confidence in this bug, but we do have a real regression.  Hopefully there is a simple explanation by just looking at the code.

:terrence, can you take a stab at this to see if anything in your code would cause tpaint (window resizing) to regression on windows 8 in e10s and pgo?

Comment 2

[Terrence Cole [:terrence]]

I've checked in a backout. I'll run Tpaint before I reland.

Comment 3

[Joel Maher ( :jmaher ) (UTC -8)]

Thanks!  Let me know if I can help at all or if you have questions on how best to use try/talos/perfherder.